The invention relates generally to computer display technology and, more particularly, to the application of visual effects using a programmable graphics processing unit. The subject matter of the invention is generally related to the following jointly owned and co-pending patent applications: “System for Reducing the Number of Programs Necessary to Render an Image,” by John Harper, Ser. No. 10/826,773; “System for Optimizing Graphics Operations” by John Harper, Ralph Brunner, Peter Graffagnino, and Mark Zimmer, Ser. No. 10/825,694; “System for Emulating Graphics Operations,” by John Harper, Ser. No. 10/826,744; and “High-Level Program Interface for Graphics Operations,” by John Harper, Ralph Brunner, Peter Graffagnino, and Mark Zimmer, Ser. No. 10/826,762, each incorporated herein by reference in its entirety.
Referring to FIG. 1, in prior art buffered window computer system 100, each application (e.g., applications 105 and 110) has associated with it one or more window buffers or backing stores (e.g., buffers 115 and 120—only one for each application is shown for convenience). Backing store's represent each application's visual display. Applications produce a visual effect (e.g., blurring or distortion) through manipulation of their associated backing store. At the operating system (“OS”) level, compositor 125 combines each application's backing store (in a manner that maintains their visual order) into a single “image” stored in assembly buffer 130. Data stored in assembly buffer 130 is transferred to frame buffer 135 which is then used to drive display unit 140. As indicated in FIG. 1, compositor 125 (an OS-level application) is implemented via instructions executed by computer system central processing unit (“CPU”) 145.
Because of the limited power of CPU 145, it has not been possible to provide more than rudimentary visual effects (e.g., translucency) at the system or display level. That is, while each application may effect substantially any desired visual effect or filter to their individual window buffer or backing store, it has not been possible to provide OS designers the ability to generate arbitrary visual effects at the screen or display level (e.g., by manipulation of assembly buffer 130 and/or frame buffer 135) without consuming virtually all of the system CPU's capability—which can lead to other problems such as poor user response and the like.
Thus, it would be beneficial to provide a mechanism by which a user (typically an OS-level programmer or designer) can systematically introduce arbitrary visual effects to windows as they are composited or to the final composited image prior to its display.